function y = tridiagal(x)
%  TRIDIA  (CUTE) Function   
%x0= [1.,1.,...,1.]..  
%fmin=n/2
%Author:shi yangyang
alpha=2.0;
beta=1.0;
gamma=1.0;
delta=1.0;
n=length(x);
y=ones(1,n);
y(1)=gamma*(delta*x(1)-1.0)^2;
for i=2:n
    y(i)=i*(alpha*x(i)-beta*x(i-1))^2;
end
y=sum(y);
